A longstanding and often heated debate in ecology concerns the number of species on Earth that will eventually disappear forever because their populations are tiny and isolated. This is a crucial question, because remaining habitats on Earth are being rapidly fragmented.

Two renowned ecologists, Stuart Pimm and Tom Brooks, have stepped into the fray with a short, lively essay on species extinction (Pimm, notably, is a member of ALERT). It's worth reading if you want to better understand the fate of Earth's biodiversity.